prometheus/vendor/github.com/peterbourgon/diskv/compression.go

65 lines
2.1 KiB
Go

package diskv
import (
"compress/flate"
"compress/gzip"
"compress/zlib"
"io"
)
// Compression is an interface that Diskv uses to implement compression of
// data. Writer takes a destination io.Writer and returns a WriteCloser that
// compresses all data written through it. Reader takes a source io.Reader and
// returns a ReadCloser that decompresses all data read through it. You may
// define these methods on your own type, or use one of the NewCompression
// helpers.
type Compression interface {
Writer(dst io.Writer) (io.WriteCloser, error)
Reader(src io.Reader) (io.ReadCloser, error)
}
// NewGzipCompression returns a Gzip-based Compression.
func NewGzipCompression() Compression {
return NewGzipCompressionLevel(flate.DefaultCompression)
}
// NewGzipCompressionLevel returns a Gzip-based Compression with the given level.
func NewGzipCompressionLevel(level int) Compression {
return &genericCompression{
wf: func(w io.Writer) (io.WriteCloser, error) { return gzip.NewWriterLevel(w, level) },
rf: func(r io.Reader) (io.ReadCloser, error) { return gzip.NewReader(r) },
}
}
// NewZlibCompression returns a Zlib-based Compression.
func NewZlibCompression() Compression {
return NewZlibCompressionLevel(flate.DefaultCompression)
}
// NewZlibCompressionLevel returns a Zlib-based Compression with the given level.
func NewZlibCompressionLevel(level int) Compression {
return NewZlibCompressionLevelDict(level, nil)
}
// NewZlibCompressionLevelDict returns a Zlib-based Compression with the given
// level, based on the given dictionary.
func NewZlibCompressionLevelDict(level int, dict []byte) Compression {
return &genericCompression{
func(w io.Writer) (io.WriteCloser, error) { return zlib.NewWriterLevelDict(w, level, dict) },
func(r io.Reader) (io.ReadCloser, error) { return zlib.NewReaderDict(r, dict) },
}
}
type genericCompression struct {
wf func(w io.Writer) (io.WriteCloser, error)
rf func(r io.Reader) (io.ReadCloser, error)
}
func (g *genericCompression) Writer(dst io.Writer) (io.WriteCloser, error) {
return g.wf(dst)
}
func (g *genericCompression) Reader(src io.Reader) (io.ReadCloser, error) {
return g.rf(src)
}